Antibiotics harm gut bacteria

Taking antibiotics repeatedly can alter people's intestinal flora and have long-lasting consequences, according to a recent US study.

Researchers found that, when people took repeated rounds of strong antibiotics, the types of microbes in their guts changed drastically.

As little as two courses of a relatively weak antibiotic is also enough to cause one set of microbes to leave the gut entirely.

Study leader David Relman, principal investigator of infectious diseases at Stanford University, said that gut communities should not be treated lightly, since they were important in the development of people's immune systems.

For the study, the researchers recruited three volunteers, none of whom had taken antibiotics within a year of the study.

The three volunteers were given two five-day courses of Cipro (Ciprofloxacin), an antibiotic that is marketed worldwide under several hundred different brand names.

Although the volunteers did not report any intestinal symptoms after they took the antibiotic, their levels of gut bacteria plummeted to as low as one-third of the normal bacteria population.

And even though it only took a week for two of the volunteers' intestinal flora to come back, the other volunteer's guts were still in disarray after six months had elapsed.

The effects were even more drastic after a second course of Cipro, with none of the participants' intestinal flora returning to normal within a week, or even a month.

Even after the study had ended, all of the volunteers still had changed gut bacteria.

Martin Blaser, a microbiome specialist at New York University Langone Medical Center, who wasn't involved in the study, said that he believed people should start paying more attention to the effects of antibiotics.

Blaser plans to make his own study of gut flora and antibiotics on children.

Gut bacteria arrive in the stomachs of newborn children within days of birth.

Some of the bacteria come from the child's mother, some from the child's father, and other bacteria comes from the child's first foods and from its immediate environment.

Other studies have shown that people who have problems controlling their weight have different quantities of certain gut bacteria than others, and that this mixture of bacteria is altered when a person loses weight.

Some scientists are convinced that autoimmune disorders are caused by alterations of gut bacteria in early childhood.

During the first two years of life, children form their unique set of gut bacteria.